Iselle Unloads Flooding Rain, Damaging Winds on Hawaii

By By Brian Lada, Meteorologist

August 28, 2016, 10:52:03 AM EDT

As Iselle moves away from Hawaii, please visit this news story for the latest information on how Hurricane Julio will impact the islands.

Iselle will continue to bring the threat of heavy rain, damaging winds and rough seas to the southern part of the Hawaiian Islands into Friday, namely the Big Island.

A second tropical system, Julio, may also bring some impact starting this weekend.

Iselle, a tropical storm, is the strongest tropical system to make landfall on the Big Island of Hawaii since reliable records began in 1950.

The storm has made landfall just prior to 3:00 a.m. HST, Friday, with sustained winds near 60 mph and higher gusts. A gust of 66 mph was observed at Volcano National Park, and a gust to 72 mph occurred at Oahu Forest National Wildlife Reserve.

Even though Iselle is now a tropical storm, the system will still pack a punch.

Rounds of heavy rain, strong winds and rough seas and surf will affect the islands into Friday night, even as Iselle weakens after passing over the Big Island. The movement of Iselle slowed Thursday night. The lower speed will prolong the effects on the islands into the first part of the weekend.

AccuWeather.com meteorologists are concerned for significant flash flooding, damaging wind gusts, mudslides and other debris flows. Ground access and communication to some communities could be cut off.

"Tropical storm-force winds will cause at least scattered power failures on the islands, including in the City of Honolulu," said Mike Smith, senior vice president of AccuWeather Enterprise Solutions.

Smith stated that based on the current forecast path and strength of Iselle, lengthy power outages are possible on the Big Island (Hawaii), where tens of thousands of customers had already lost power as of early Friday morning.

"Multiple roads could be washed out on the Big Island, Oahu and Lanai," Smith said.

Rainfall will average 2 to 4 inches over the islands with locally higher amounts, especially on the eastern slopes of the islands, particularly on the Big Island. These slopes could receive locally 12 to 24 inches of rain.

Bathers, boarders and boaters should exercise extreme caution, even as the system weakens while negotiating the islands. Small craft should remain in port as waves in unprotected waters will range between 15 and 25 feet.

According to AccuWeather Hurricane Expert Dan Kottlowski, "Wave action along the eastern and northern coastline of the islands, especially on the Big Island, can lead to damage from flooding and erosion."

"However, as Iselle continues to track toward the west, a southwest flow may bring higher-than-normal surf to west- and south-facing coastal areas, as well as significant rainfall on the south-facing slopes of the mountains."

Visitors and residents alike should check the conditions as the storm will continue to cause rough surf and rip currents.

The Big Island of Hawaii has taken a direct hit from the storm before passing just south of the smaller islands, such as Maui or Oahu.

A direct hit on the other islands does not have to occur for significant impact as the storm is much larger than a single point of latitude and longitude.

Some portions of the islands that typically receive little rainfall could be hit with flash flooding.

Hawaii residents and tourists have been rushing to stock up from not only Iselle, but also Julio. The high demand for water and other basic supplies has created massive crowds at stores and stocks have dwindled.